Flanges, also known as raised face flanges or rim flanges, are components used to connect shafts to each other, typically for joining pipe ends; they are also used at equipment inlets and outlets, such as reducer flanges. A flange connection or flange joint refers to a detachable connection formed by the combination of a flange, a gasket, and bolts as a sealing assembly. Pipe flanges are those used in piping installations, while equipment flanges refer to the inlets and outlets on equipment. Flanges have holes and bolts that secure them tightly together, with a gasket used between them for sealing. Flanges come in threaded (screwed) connections,焊接 (welded) flanges, and clamp flanges. Flanges are always used in pairs; low-pressure pipelines can use threaded flanges, while those over four kilograms of pressure typically use焊接 flanges. Two flange discs are joined with a sealing pad in between, then secured with bolts. Flanges of different pressure ratings have varying thicknesses and require different bolts. Equipment like pumps and valves, when connected to pipes, have corresponding flange shapes at their local connections, also known as flange connections. Any connection component that uses bolts to join two flat surfaces while sealing is generally called a "flange," such as in ventilation pipe connections. Such components can be referred to as "flange-type parts." However, this type of connection is only a part of a single device, like a pump connected to a flange, so it's not appropriate to call the pump a "flange-type part." Smaller items like valves can be called "flange-type parts."